1. Field of the Invention
The present invention relates to a method for subjecting a trim cover assembly to foaming by injecting and curing a liquid foaming material therein, to thereby form a foamed product integral with the trim cover assembly, such as a headrest and armrest for use with an automotive seat.
2. Description of Prior Art
Seats, headrests, armrests and other cushiony accessories for use in automobiles are basically formed from a trim cover assembly and a foam padding. In particular, a typical process for forming a relatively small article, such as headrest or armrest, involves a foaming step wherein a liquid foaming material is injected and cured in a three-dimensional trim cover assembly to create a foam padding fill therein, together with a framework and some fittings if required, so as to produce a resulting foamed product integral with the trim cover assembly (e.g. headrest or armrest). In most cases, the three-dimensional trim cover assembly used is preformed by sewing together plural separate cover sections, each comprising a top cover layer (or surface cover piece) and a thin foam layer (or slab foam wadding piece), into a predetermined three-dimensional or box-like configuration that conforms to an outer shape of a resulting product.
In this kind of trim cover assembly, a natural or artificial leather material is sometimes required as the top cover layer thereof. Typically, the natural leather material includes a bull leather, a horse leather or the like, and the artificial leather material includes a synthetic resin leather or the like. In that instance, conventionally, a piece of leather surface cover material, be it of a natural or artificial leather, is adhesively laminated at its reverse side to a piece of thin foam padding to create one cover section unit which forms a part of a resulting three-dimensional trim cover assembly. However, in this particular lamination process, an adhesive is applied to whole areas of both leather surface cover piece and foam padding piece to thereby provide a bonded cover section unit. Such bonded cover section unit will inevitably cause objectionable wrinkles and creases therein when it is bent and curved by a worker for sewing with another bonded cover section unit (s). Further, in most cases, a plurality of the thus-bonded cover section units are first set in a reversed state where the foam padding layers thereof are exposed outwardly and then sewn together to form a reversed state of three-dimensional trim cover assembly (generally conforming to an outer shape of headrest or armrest, for instance) wherein all the foam padding layers are exposed outwardly while the leather surface cover layers are situated in the interior of trim cover assembly. Then, such reversed trim cover assembly is turned over from an opening thereof into an normal state where all the leather surface cover layers are exposed outwardly. This reversing process further causes additional wrinkles and creases in the resultant trim cover assembly, which impairs the aesthetic appearance of leather surfaces thereof.
To solve the problem, instead of the foregoing full lamination, it has been proposed to effect a partial connection between the leather surface cover piece and foam padding piece. That is, the peripheral end regions of the leather surface cover piece is adhesively attached or sewn along and with the corresponding peripheral terminal ends of foam padding piece to form a partially joined cover section unit. But, when a plurality of such cover section units undergo the abovementioned bending and curving by a worker in sewing them together and also undergo the reversing process for reversing the trim cover assembly into a normal state, the foam wadding layers are floated and waved from the leather surface layers, thus creating plural creased and bent areas in the foam wadding layers. Eventually, when subjecting the thus-formed trim cover assembly to a foaming process, there are a plurality of incompletely foamed spots at those creased and bent areas in the foam wadding layers.
In view of the above-stated drawbacks, it is therefore a primary purpose of the present invention to provide an improved method for forming a foamed product integral with trim cover assembly which insures to avoid creation of slack and crease in both of surface cover pieces and foam padding pieces of the trim cover assembly.
In order to attain such purpose, in accordance with the present invention, there is basically provided a method comprising the steps of:
forming a plurality of surface cover pieces in a predetermined shape, each having ends;
forming a plurality of foam padding pieces, each being small in size relative to each of the plurality of surface cover pieces and having ends;
juxtaposing each of the plurality of foam padding pieces on each of the plurality of surface cover pieces;
bringing the ends of each of the plurality of foam padding pieces in alignment with the ends of each of the plurality of surface cover pieces;
then, sewing the ends of each of the plurality of foam padding pieces with the ends of each of the plurality of surface cover pieces, thereby forming a plurality of sewn cover sections required to form a trim cover assembly in a predetermined three-dimensional shape;
thereafter, bending and sewing together end portions of the plurality of sewn cover sections such that the thus-sewn bent end portions of sewn cover sections face to a side where the plurality of foam padding pieces lie, thereby forming the trim cover assembly in the predetermined three-dimensional shape;
injecting a liquid foaming material into inside of the thus-formed trim cover assembly where the plurality of foam padding pieces face inwardly thereof;
curing and expanding the liquid foaming material so as to create a foam cushion member filled in the trim cover assembly, whereby the foamed product integral with the trim cover assembly is formed,
Accordingly, due to the difference in size between the surface cover piece and foam padding piece, each of the foregoing cover sections has a slack region created in the surface cover piece relative to the foam padding piece, but the step of bending the ends of such cover sections is effective in stretching the slack region uniformly on and over the foam padding piece, thus avoiding creation of any slack and crease in both of the surface cover and foam padding pieces in the resulting foamed product. This is particularly effective in the case of the surface cover piece being a natural or artificial leather material. In other words, considering the nature of leather material which is easy to be slackened and creased, the foam padding piece is small in size to the leather surface cover piece, and all the peripheral ends of the foam padding piece are aligned and sewn with all the corresponding peripheral ends of the surface cover piece to create a slack region in the latter in advance, so that, subsequently, such slack region are stretched and juxtaposed uniformly and neatly on the foam padding piece by bending the thus-aligned and sewn peripheral ends of both two pieces at substantially a right angle relative to given bending lines.
In one aspect of the invention, the plurality of surface cover pieces may each be formed in a predetermined shape so as to have outwardly arcuate end portions and four corners, whereas each of the plurality of foam padding pieces, which is small in size relative to each of said plurality of surface cover pieces and has ends, may be formed such that the four corners thereof are diagonally equal to the respective four corners of each of said plurality of surface cover pieces. In that case, each of the plurality of foam padding pieces may be juxtaposed on each of the plurality of surface cover pieces in such a fashion that the four corners of each of said plurality of surface cover pieces match the respective four corners of each of said plurality of foam padding pieces, while the outwardly arcuate end portions of each of the plurality of surface cover pieces project from and peripherally of each of the plurality of foam padding pieces. Which will make it more easy to locate the foam padding piece relative to the surface cover piece and effectively create a proper slack region in the surface cover piece in the cover section which is obtained by sewing together the peripheral ends of both foam padding and surface cover pies as stated above.
Other various features and advantages will become apparent from reading of the descriptions hereinafter, with reference to the annexed drawings.